For centuries, maybe even millennia, people have burned plant material, such as for example tobacco leaves, in order to inhale the smoke to realize a physiologic effect from one or more compounds contained within that smoke. However, this burning process comprises a high temperature oxidation that produces many chemical compounds not present in the original material. Certain of those new compounds are unhealthful and/or carcinogenic.
Dried tobacco leaves, for instance, contain approximately 300 different chemical compounds, yet, when combusted, the resulting smoke contains approximately 5000 different compounds. Many of the oxidation products are known to be unhealthful, such as carbon monoxide (CO) and the family of polycyclic aromatic hydrocarbons (PAH's). In addition, in the elevated and uncontrolled temperature of combustion, many of the desirable compounds, such as nicotine, are destroyed. As a result, a large quantity of the original material is needed because much of the desired compound(s) are destroyed in the combustion process.
The desirable compounds in the smoke are not in fact created in the combustion process, but rather exist in the plant material in its natural state. The combustion process serves only to vaporize those desired compounds. A more healthful alternative to combusting the plant material as a means to release its active or desired constituents exists. Applicant's method heats plant matter to a temperature just below combustion temperature for cellulose of 450 degrees Fahrenheit, thereby generating an aerosol comprising the desired compounds.
U.S. Pat. No. 4,303,083 teaches an electrical device similar in appearance to an ordinary tobacco pipe in which the tobacco is placed directly in the electrically heated bowl, and the amount of heating is controlled by the setting of a variable resistance heater. The '083 patent illustrates the problem inherent with conductive heating, namely the non-uniform heating of the plant matter. The tobacco in direct contact with the heating element gets much hotter than other tobacco disposed farther from the heating element. Such non-uniform heating burns some of the tobacco, while at the same time inadequately heating other portions. In addition, the invention of the '083 patent is deficient because the amount of heat energy delivered will need to be adjusted based on varying inhalation rates.
U.S. Pat. No. 6,095,153 teaches a device which uses a heater to heat air to a selected temperature, and maintains that temperature within a narrow range. However, in order to maintain that narrow temperature range, the invention of the '153 patent necessarily comprises a large thermal mass, which requires a considerable warm-up time. In addition, such a large thermal mass results in an undesirable bulky and heavy apparatus, which adversely affects portability.
U.S. Pat. No. 6,513,524 teaches an apparatus for generating volatized vapor from different materials, and a way to collect and removeably distribute the gathered vapor. This device comprises a base unit which requires utility power, and is therefore, non-portable. In addition, the invention of the '524 patent is inconvenient to use because the user must manually set the amount of heat energy generated, meaning the user will have to go through a process of trial and error to determine the optimum setting. The device also requires considerable setup time, in waiting first for the unit to preheat, and then for a bag to fill with vapor and then cool.
U.S. Pat. No. 5,865,185 teaches a smoking article in which a replaceable tobacco flavor unit containing tobacco flavor material is electrically heated by a set of permanent reusable heaters to evolve flavors or other components in vapor or aerosol form for delivery to a smoker. Each heater heats only a portion of the available tobacco flavor material so that a plurality of individual puffs of tobacco flavor substance can be delivered sequentially to the smoker. This article makes no attempt to control or limit the temperature to which the tobacco is subjected, other than limiting the applied energy, which is applied in a conductive and radiative sense, and therefore stands a very high chance of delivering combustion products to the user, along with the tobacco flavor.
Accordingly, several objects and advantages of Applicant's invention are the following: more uniform heat distribution, greatly reduced chance of combustion, faster warm up time, greater portability, greater ease of use, and simplification of manufacture.